Automatic train-speed-control system for railroads



Feb. 25, 1930. w. H. RICHARD 1,748,922

' AUTOMATIC TRAIN SPEED CONTROL SYSTEM FOR RAILROADs Flai.

w. H. REI'CHARD AUTOMATIC TRAIN SPEED coNTRoL SYSTEM Fon RAILnoAns Feb. 25', 1930.

Filed May 21. 1925 ,2 Sheets-Sheet mol D S. R. om mr NVE TOR.

iofPlOyed 011 the,

" track rails.

Patented Fa). 2s, 1930 iUNITED STAT-Esp.

y vi1,7i48,922y

i? lATENTg SIGNAL COMPANY, 0F` ROCHESTER, NEW' YORK AiiioiViArro vTRAIN;si?inni) ooiv'riaon SYSTEM-Fon. RAILROADS Application inea may ci,

This inventionrelates to automatic train control systems for railroads,'and more par-f ticularlyvto thatt'ype of system now com-` v vmOnly-knownasacontinuous controlsystem, l `935which employsI alternating current in the' track rails and controls inducti'vcly electroresponsive means on the'car'. j

l In one type of the so called Vcontinuous control systems, a three-position relayv is em- Y locomotive, and this relay'is vcaused to assume lany one of its three dinerent positions, in accordancewith traffic conditions, by the control of the flow of alternatingcurrent in two .circuits includingjthe One of the currents in the track rails, conveniently termedthe track phase or loop circuit current, flows in the track rails il) opposite directions atany given instant, like the ordinary track ycircuit current. The othery 2o current, conveniently called the line phase or y.tion relates to the provision ofnieansiforausimplex circuit current, flows in the twotrack rails Vin multiple and is displaced 'in 'phase with respect to the track phrase current, y y A vsystem such as justdescribed provides l for.V three distinctiveinfluences ,or controls,

available for' enforcing three 'differentjspeed limits, for example, .or `for other lautomatic control as maybe considered necessary. In

applying automati traincontrol to iailroads,V however, it is found desirable, morder t'o provide automatic control of trainimovements efficiently and with 'the least 'delay,'to have y vmore than three fixed speed limits. )In short, it is found expedient to be able tQfSet at '35 any desired point along the railroad,l under a given'traiiic condition, any particular speed l l p f y n y y Y obJectsandladvantages of the invention lwill limit desired. n y y l y In order to provide such,desirablefflexibility and to make ,availablejaf relatively' large signa-ie..

i925. 'seriaiiia 31,840. y

bility ofrs'peed 11m-iis is employed toV aavan tage, particularly uin providing a tapering, speedcontrol to enforce obedience to caution .Y train traveling in a .dangeror occupied vblock should not, forreasons alreadvunderstood bythose familiar-with the art, exceed some predetermined low or. minimum speed limit, such as 15 orjQOiiniles per hour. Since such minimum speed limitk is lto'be continuously'imposed', and jmay'bethe same for" all blocks, it is proposed in accordance with this invention yto Vemploy la speed-responsive YVdevice drivenfrom thecar wheels, in conjunc.-- Y

tion with associated controlling mechanism, toprovide such "minimumzspeed limit, and

`,arranged to lapply, thebrakes if that 4'speed ilimit is exceeded at :any point in saidldanger 'A further Vfeatui '"`e or object of' this inventin Signat `er .Collsrendifne sbntfol point, unless 'the engineer takes appropriate action',

conveniently termed acknowledgment, in recl'ognitionof the caution indication and asa 'manifestation 0f; his vglrie A1665 if is proposed to` freqriirje such acknowledgment upon the `approachY toa stop signal,siicht'tc- 8o ybein part apparent and in part more fullyexplained asthe descriptin ,progpresses.,V

One speciic embodiment ofthe invention 40 lnumber of speed limits from which .tofs'elecn it is proposed in accordance with the present invention to utilize the time-distance interval principle `in connection withV continuousinductive control systems, and'to `provide for the automaticapplication of the brakes' at v anyfs'elected point alongl the track if'a train exceeds any predetermined speed limit at that point as may be selected orfound expe- Y dient, under clear, caution, yor danger traffic D conditions, as may be required. This fie-xi- 'has been selected in describiiigthis particular embodiment referer'icey will beV meile tothe accompanying' drawings, infwhich Fig. 1 lshows the track equipment and aip'r* tion of the car equipment, togetl'ier withsine 9 braking 'curves and speed .limitflines *illus* trate@ t9 fesiltteexplahatiii; and

2' 'shows'ierapibaraws ifnis. 'with'the exceptioi'ioffthe oeils and Vamplifiers illustrated vin Fig; '1. 100

the particular construction and arrangementof parts and circuits that might be used in practice to the best advantage.

Tmclcwag/ equipment Referring to Fig. 1, the track rails 1 are 'ided by insulating joints 2 into blocks in ual way and in conformity with recogblock signal practice. Only one complete block C and the adjacent ends of two other blocks B and D have been shown. The partsand circuits associated with each of the several blocks are assumed to be the same, and tor convenience corresponding parts will be given the same reference characters with distinctive exponents.

Extending along the trackway is a transmission line TL, supplied with alternating current,.preferably ot' a commercial frequency, such as cycles, from a suitable source iniicated as a generator 3. The use ot alternacing current track lcircuits is assumed tor the particular embodiment illustrated; and the secondary of a track-transformer et is connected across the track rails lat the exit end of each block, said connections including a limiting inductive reactance or impedance 5. Associated with each block is a track relay T; and as shown this track relay is of the two element or polyphase type shown in accordance with established convention. The track phasewindingof the track relay T is connectedfacross the track rails at the entering end of each block in the usual lway; but

the local phase winding 6 of each track relay,

instead of being directly connected to the alternating current supply, in this instance is connected in a circuit including the secondary of a transformer 7 and a front contact 8 of a check or safety relay 9. which is preferably a single phaseY relay of suitable construction. Y

Across the track railsl at the entrance end ot each block is connected a non-inductive balancing resistance 10; at an intermediate point near the exit end of the block is a Similar resistance 11 and at the exit end of the block is another resistance 12. The intermediate point in the block, at which the balancing resistance 11 is located, is convenient-ly referred to as the point B; and this point B is braking distance from the exit end ot the block for the low or minimum speed selected, assumed to be about 20 miles per hour. Alterna-ting current is impressed across the middle points of these resistances 10, 11 and 12 of diEerent relative instantaneous polarities under different tratc conditions, under the control of the line voltage.

track relay oi the next block in advance. As shown, a transformer 13 is used for supplying current to the line phase or simplex circuits of each block. y

Under clear traffic conditions, alternating current of the normal instantaneous polarity is supplied across the middle points ot the balancing resistances 10 and 12 by a circuit which may be readily traced as follows commencing at one terminal of the secondary of the transformer 131, limiting resistance 141, tront-contact 151 of the track relay T1, wire 16, balancing resistance 12, along the track rails, other balancing. resistance 10, wire 17, check relay 9, wires 18 and 19, front contact V201 oi track relay T1, and wire 211 to the opposite terminal of said secondary.

Under caution traiiic conditions, that is, with the block next in advance occupied, alternating current of thereverse instantaneous polarity israpplied across `the resistance 10 Y and 11 and through the line wire including rails 1 in multiple, balancing resistance 11,

wire 23, back contact and contact linger 201 of track relay T1, and wire 211 to the opposite terminal ot said secondary. i

Thus, under clear tratlic conditions the line.

phase current of normal polarity is supplied throughout the lengthot the block between the balancing resistances 1Gand 12; whereas, under caution conditions, this current is of reverse polarity and is between resistances 10 and 11 only, said line phase current also flowing through the track loops L. In a danger or occupied block, the iiow of line phase current is not changed from normal, unless the block next in advance should also be occupied; but in such occupied block the track phase current is cut oli from a following train by the shunting action of the wheels and axles of the leading train in the block. i

The line phase or simplex circuitvcurrent flowing in the track rails in multiple is preterably made resistive with a Iminimum i amount of inductive reactance, so that the current is nearly in phase with the transmission line voltage; and the track phase or loop circuit current, flowing down one rail and back the other at any given instant, is on the other hand made reactive so that the current therein lags with respect to the transmission Such phase displacement of the current in the track phase and line phase may, however, be obtained in other Ways.

'-{Trackway block signalsof a suitablel type Z is shown at the entrance to Veach block, no attempt being made'to illustrate its control circuitS, ,Which may be of any suitable form nowl `commonly used in automatic block signalling.

The track Zoop Y track loop comprises a wire or-cable with a Vheavy vinsulating body of suitable material protected from mechanical injury andweatlr" er, which is fastened by-suitable clips against theV webv of thev rail.. AThe wire of vthe track loop may be inclosed in a metal conduit bolted against the web of the rail underneath the head. As shown, each track loop consists of onerun or turn adjacent to the track rail, but

`a plurality of turns are used to advantage in most instances, the other side of each run or turn being at some distance from the rail so that its magnetic field 'will' not materially vinfluence the receiving coils on the locomotheir circuit connections. 'lhis car apparatus includes a suitable speed responsive 'device SD, driven from the car wheels; and this devi'ce SD acts toopen contacts atV all speedsf."

tive. ,'The `various loops atdifferent points along'fthe track arediiferent in length corresponding to the particular speed limit it is desired'to enforce." These track loops are j conveniently..referred toas speed loops.; and" asV shown, there are three speed loops L, L1'

Vand L 2 for the block C.

Y Oar equipment rIlie influence receiving equipment'for the car, showny diagrammatically in Fig. l, com- `prises two receiving coils l? and P1, Vwith or with-out laminated iron cores, which are carried overopposite track rails at the front end and in the rear ofthe engine andtender. These coils are resonated by condensers inthe usual Way and are connected to the inputcircuits of suitable amplifiers A and A1, the output lcircuitsy of 'which are connected to the field windings 26 and 27 of a two element or polyphase alternating current relay of the vane or rotor type. This main car relay MR Iis provided with contact fingers in theusnal way vand is biased to a neutral or de-energized position. One'finger is shown in Fig. l; and this finger is moved'to one eXtreme position with both' field windings 26 and 27 `energized Vwith currents having one phase relation, is shiftedY to the other extremey position when both field windings are energized but with ythe current of one field winding reversed,

and to the (ie-energized positiony when either or both of the field windings are de-energized. y .y

Inaclear block, the track phase and line lphase currents supplied to the rails have the normal 4phaseJ relation, and the contact fin- V,gers of the main car relay MR assume one eX- treme position, shown in full lines, conveniently called the normal'position.v In that portion of a cautionv block in the rear of the v,point B, both track phaseand line phase currents' are owing, but these currents have an.

opposite phase relation; and the contact Vfingers of the main car relay MB assume the other extreme or reverseposition. ln a caution block between the point B and theend yof the block', the line lphase current is cut o, de-

`isshunted by the wheels and 'axles of the forward train, .thereby de-energizing the field 3 winding 26 of the relay MR on the following train, andcausing its contact lingers toasl Vsume, the neutral or de-energized position.

This operation, tliusbriefly outlined, is characteristicof the typical B-position continu-l ous inductive control system, employing track phase and line phase, and a point B; and beno detailed explanation.

' Fig. 2 shows diagraiiimatically the partsg ing familiar to those skilled in theart, needs` of the car-carried apparatus, together withv` above some selected minimum speed, such as 18 or 2() miles per hour. rlhis speed resp'onto the car wheels or axles; and at speedsfabovev the minimuml speed, this centrifuge moves a` contact disc 29 out of engagementwvith cooperatinginsulated contact springs 30. l

ln addition tofthe'main car relay MR, already described, the car apparatus'inclu'des four other relays preferably of the direct lcur-y rent tractive type, which are suitably constructed in a manner forming no part of the Vpresent invention so as to open and close their contacts indifferent time relations with respect to the opening and closure of their en its contacts upon deenergization thereof-A after a longer time interval, assumed tol be one and one-half seconds. The relay'TU is a slow pick-up relai ,i and when energized i'equires a certain intervalof time, assumed to be yabout .one-half second, to close itscontacts VV.ergizing circuits. The relay S is a slow re afterclosure of its energizing circuit.y Thev relay Q, is quick acting, closing and opening energization thereof.

The car apparatus also includes a manually 'its contacts quickly upon energization and deoperable device, lconveniently termed an acknowledging contactor, which is located in the cab within reach of the engineer, and is intended to be operated by the engineer every time a caution or danger signal is passed or corresponding cont-rol takes eiiect, such manipulation on the part of the engineer constituting an act of acknowledgment in recognition of the unfavorable change in traiiic conditions. In the simplified form shown, this acknowledging contactor AC comprises a plunOer 31 supported in suitable guides as 32, which is urged to the upper extreme position by a'spring 33 between the guide 32 and a collar 34 on said plunger. A pivoted lever or handle 35 has one end engaging the collar 34, so that when said lever is raised the plunger 31 is moved downward. rlhe plunger 31 carries two insulated contact discs or members 36 and 37 which bridge cooperating contacts (indicated conventionally as arrows) when the plunger is in its lowermost position. One end ot a lever 38, pivoted at an intermediate point, rests upon the upper end of the plunger 31, and the other end of this lever is pressed upward by a spring 39, bearing against a suitable stop. The spring 33 is stronger than the spring 39. rlhe rocking movement of the lever 38, in response to the expansion of the spring 39 upon downward movement of the plunger 31, is retarded by a suitable timing device, which in the 'orm shown comprises a rod 40 pivotally connected to the lever 38 at one end and to a piston 41 with a flexible packing at the other end. rlhe piston 41 works in a cylinder 42 havinga restricted oriiice 43 in the upper end. It will be evident that the upward movement of the piston rod 40 is glradual, depending upon the slow escape of t e coniined air through the oriiice 43, but the downward movement is quick, air passing readily upward past the piston 41. Vhen the lever 38 has beenrocked by its spring 39 to an extreme position, its end opens a pair of contacts 44.

1t will be observed that this acknowledging contacter AC is essentially a manually operable circuit controller by which two circuits may be closed at the contact members 3 6 and 37, and that, if the contactor is held in its active contacting position for more than a predetermined interval ot time, other contacts 44 are automatically opened. Obviously, other combinations and arrangements of devices inay be employed to attain these functions; 'and it should be understood that the particular construction of acknowledging contactor diagraminatically shown is merely illustrative.

It is assumed that the usual air-brake equipment is automatically controlled to produce a brake application by means of an application valve AV, in turn controlled by an electro-pneumatic valve EPV. Various forms ot automatic brake control devices may be employed; but in the particular arrangement shown, the brake control device or application valve is'of the type shown, tor example,'in the patent to 1V. V. Turner, No. 1,309,787, July 15, 1919. This type of application valve AV comprises a piston 45, with a restricted opening 46 therein, the left hand side of which is exposed to main reservoir pressure, and the right hand'o-f which isacted upon by a spring 47. The enclosed chamber 48 on the right hand of the piston 45 is connected by a pipe 49 to an enclosed chamber 50 in the lower part of the electro-pneumatic valve EPV, this chamber 50 also communieating with a timing reservoir 51. The electro-pneumatic valve EPV is ot any suitable slow acting type of construction; and when its coils are energized, it holds a valve 52 seated, and when cle-energized, permits this valve to be opened by a spring or air pressure and exhaust the chamber 50 to atmosphere through an exhaust port 53. The slow action may be obtained by use of copper rings around the core o-r other expedients.

Also connected to the chamber 48 on the right hand side of the piston 45, by a pipe 54, is an expansible pressure responsive device 55, which in the form shown vcomprises two ends connected by metallic bellows, one

end being xed and the otherend movable.

Y The movable end is connected to ar0d56 which carries insulated contact members 57 and 58 arranged to engage contacts (shown as arrows) when the bellows of the device 55 collapse upon release of pressure therefrom, due to the resiliency of the bellows themselves. In short, contact members 57 and 58 are inthe open position when a predeter: mined pressure exists in the chamber 48 and are closed when this pressure drops to a certain value.

The car apparatus also includes suitable cab signalling or indicating means, which may take the form of lamps of different colors, or lamps illuminating backgrounds having diiierent letters or insignia thereon, or any other suitable form. ln the simpliied form shown, it is assumed that three lamps will at times be lighted to illuminate suitable letters such as G, Y and R, corresponding to different train controlling conditions.

Operation The operation is most conveniently described and explained in connection with various assumed trai'ic conditions. Assume that the train is traveling in a clear block, the contact fingers of relay MR being in the normal pcsition'shown, and the other parts and circuits being also inthe condition shown in Fig. 2. For simplicity, various Vcircuits have been shown as extending from one point, designated B, indicating a connection to one terminal of a car battery or other suitable source to another point, C, Vindica-tingy connectionY to the outer terminal ofthe battery.

Under normal conditions,the electro-pneu;

,matic valve EBV is venergized by a circuit which may be traced as follows :,-commencing at yl3,fcontact finger of the relay normal, wire 61, contacts 44 of the acknowledging contactor, wire 62, winding of valve With the contact finger'63 of the relay or indicator G is 'lighted by a circuit, which will be obvious. With the contact finger 6 4 of therelay MR inthe normal position, the slow pick-up relay TU is energized bya circuit as follows :--commencing at B, contact nger 64 normal, wires'65 and 66, relay- TU'toC. .A l .c Y l Assuming the parts in the normal position shown and the train traveling at some speed l abovetheminimumsspeed, Vso that/the speed contacts294-30y areopen, suppose that the train lpasses from a clear blockv into a.cau'

' tionblock, the'contactufingersfof the relay f ing thatthe engineer acknowledges properly,y

i MR shifting 'from .the normal position to the reverse'positionfV lf the engineer is vigilant inithe observance ofthe wayside signals, he

will know when histrain isabout .to enter a caution block; and as a manifestation that he is alert andrecognizes the existence of unfavorable traffic'conditions ahead, he is required to operate the acknowledging contactor AC. He must do'this before the trainr enters the cautionfblock and the relay MRy assumes its reverse. position, thereby deenerfgizing the relay TU, which opens its quickly upon its de-energization. vAssumupon depression of theV plunger Slto move the Contact iiiember37`int`o engagemen't'with its contacts, anenergizing circuit for the'V relay Q is established, asy follows :'-commencing at B, contact finger 67 and its front con-.

l tact *.ofrelay TU, wires' 68v and 69, contacts 37, vWires 70 and 71, relay Q, land wire 72 to C,4 The relay Q at once closes itsf-ront contacts; and when the relay MR is reversed, and

the relay TU is vde-energized, a circuit-for maintaining the valve EPV energized is established as follows t-icommencing at. B, finger67 andthe' back contactyof relay TU,`

' wire-7 3,"firiger 174 lof relayQan'd its front" w1fes1-75 aaa17e, ,contacts n of' `acknowledging; .contactor,` wire 62, valvel EPV toC.'` The valve EPVis made slow acting, Vas previously, explained, so that it willnotopenjand apply `the brakes during theA short interval oftimey intervening between'the fopeningof its normal energizing Circuit at "the 'ingerO of the relay 'MR, land its normal contact. and the closure 3 ofv the vauxiliary [energizing circuit just traced.

A'fter'l'the relay has .been energized'in this manner, itis maintained energizedby a stick in the normal position,'tie ycab signal 'lampvv contacts relay MR remains in the reverse position, this stick lcircuit being traced as follows com- Y mencing at B, finger 68 reversedpwre 78,` finger 79 of relay Q and ,its front contact,

wires 80, 8l and 7l, relay Q, wire 72 to C.

lf the engineer fails to acknowledge the caution signal properly, and therefore fails topick up the relay Q, thenthe valve EPV -j is cle-energized long enough to open,vwhere upon pressure is 'exhausted from the chainber 48 through the exhaust port 53 much faster than it can be suppliedthrough'the 'Y small opening 46, in said piston, thereby causing said piston to be shifted to the right yin opposition tothe spring 47 and produces an automatic brake application; When thepresfsure drops inthe chamber. 48, the contacts 57 and 58 close.l VIf the engineer then operateshis acknowledging contacter AC, the relay Q is lenergized by a lcircuit as follows commencing at B, contacts 58,

wires y77 andy 69, contacts 37 of acknowledging contacter, wires 70 and 7l, relayQ and wire 72 to C. The'car relay MR being in the reverse position, the relay TU is de energized; and with this relay Q energized,V

the valveEPV-is energized throughout the circuit-hereinbefore traced, through the back Contact of linger 6 7 of relay TUvand front contact of finger 74v of relay Q.

Although such re-energizationl of thevalve:

EPV closes Vthey exhaust from the chamber V48, nevertheless the piston 45 doesnot'at once returnto the normal position shown and permitthe release of the brakes, becausethe pressure must equalize onvopposite sidesof Y the piston before-this 'can happen; and on n accountfof thetiming reservoir 51, it takes some time for the pressure, Vflowing through the small hole 46 in the piston 45,1150 build up to normal. Consequently, irrespective of `restoration ofr the valveEPV, lthe brakes cannot be released'for a time; and this time interval is selected to'be long. enough to as sure stoppiifigy of the train. It is preferred to permit release of the brakes after altime in this way, rather than by Voperation of fa reset'device, accessible only froml the ground because of the diiiiculty in locating such areset device so that it can not be improperly manipulated, and also'can be easily ymanipulated Vunder alll conditions encountered in practice, such as intunnels, on'rtres@ tles vand-the like. Itwill be: observedfthat the release of the brakes does not take place.v automatically,buty only after theengineer has vmade a positive act by operating his acknowledgingcontacter, Y

Sr limit@ a arretrate@ phase current as is flowing in both rails and produces upon the receiver P1 the same resultant effect as if the line phase current were again reversed, that is, were of the normal instantaneous polarity. In other words, with the train moving in a caution block the instantaneous direction of flow of current in the receiver P is actually reversed each time this receiver is under a loop L; this because the current in the loop wire is substantially again as large as the current flowing in the lower rail l, so that loop current not only neutralizes the effect of the rail current but actually predominates thereover to a suliicient degree to operate the relay MR to to a normal position. The speed loops may have any desired number of turns to accomplish this end, it being, of course, evident that only one side of each turn should be close to the track rail.

At the time the train approaches a speed loop in Va caution block, assuming that no automatic brake application has previously occurred due to failure of the engineer to acknowledge or due to excessive speed, the relay Q is energized by its stick circuit; the relay TD is maintained energized by a circuit through the linger 64e of relay MR', wire 82, relay TD and Wire 83 to C; the relay TU is de-energized; and the valve EPV is maintained energized by its auxiliary holding' circuit hereinbefore traced. When the contact lingers of the car relay MR shift from the reverse vto the normal position as the train comes over a speed loop, the relay Q is de-energized on account of the opening of its stick circuit at the finger 63; and while the lingers of the relay MR are in the nor-- mal position, the valve EPV is maintained energized by its normal circuit through the finger 60 of relay MR and its normal Contact. Obviously the green lamp G will be energized so long as the relay MR is in its normal position upon passage of the train by a loop L. During the movement of the main relay MR from its normal position to its reverse position upon leaving such loop the relay Q-willV remain in its energized position long enough to allow its stick circuit to be completed through contacts 63 and 7 9, this by reason of the fact that its pick-up circuit through the armatures 84 and 87, tov be described below, is not immediately broken upon such change in the relay llIR and also because a certain amount of time is required for the relay Q to drop. The relay TD is cle-energized, but does not open its front contacts until after one and one-half seconds; and the relay vTU is energized, but does not closeA its front contacts until aftera half second.

Assume that the speedof the train is low enough so Vthat the rear receiver P1 does not. leave the speed loop until after the lapse ofV one-halfsecond, giving the relay TU time to close its front contacts, the front contacts of they relay TD not yet having opened. Under these conditions a pick-'up circuit forthe relay Q is established as follows z--commencing at B, finger 84C of the relayTD and its front contact, wires 85 and 86, linger 87 of relay TU and its front contact, wires 88, 8l and 7l, relay Q, and wire 72 to G.- Then, when the contact lingers of the relay MR return to the reverse position after the train passes off of the speed loop, the stick circuit for the relay Q is established, and upon deenergization of the relay TU, the auxiliary holding circuit for the valve EPV is established, and no brake application occurs. In other words, the relayT Q is -de-energized at every loop L and is again picked up if the speed of the train by'such loop is low enough to allow sullicient time for the relay TU to pickup and complete the pick-up circuit for relay Q just traced. In this connection.l it should be remembered that during the passage of the vehicle by a loop L the normal circuit for the device EPV is closed. The i operation is similar tothat occurring when the engineer manually acknowledges, but this operation occurs automatically, provided the slow pick-up relay TU has time to close its front contacts during-the interval of time intervening between the reversing of the contact lingers of the Vcar relay MR.

If the speed of the train is such that the relay TU does not close its front contacts before the fingers of the car relay .MR return to their reverse position, then the valve EPV is de-energized, its normal energizing circuit being broken at the finger 6() ofthe relay MR, and its auxiliary energizing circuit being broken at thelinger 74 ofthe relay Q, which has not been re-energized. Consequently, an automatic brake application occurs, and the bra-kes cannot be released until after operation of the acknowledging contactor an-d the lapse of a predetermined time, the same as previously explained.

From this explanation it will be evident that any desired speed limit maybe enforced at any desired point along the track in a caution block by installing a speed loop at that point having a length Vcorresponding to the speed limit desired.V For instance, assuming one-half secon-d timing for the car appa- Vratus, a speed loop of 22 feet would result in underi automatic brake applications, and al speed-'distancebrake application curve. The brake Aapplication curve shows the speeds at the various points in the block at which, if

the valve EPV opens and initiatesan automatic brake application, such brake application will cause the train to follow the braking tiene@ beforereaching the end ofthe block.,y As-` l highthat a brake application occurring 1n the suming the use of; three speedloopsfL, L1y and; L2 spaced approximately asillustrated, thelength of thexiirst loopL should be such as 'to enforce a speedlimit not greater than the speedv indicated by the point onvthe applicationcurve 90 corresponding` tothe locationo the next speed loop L1,.so-that a train cannot passl the firstrloop Latvany speed so nent speed loop L1 will fail to stop the train short of theendrof the block, thepossibility of the train accelerating between speed loops being taken into account if desired. TheA sameexplanation applies to the Vlength'l of thel secon-dloop L1. The speedv` limit for the lastvloop L? in the block is preferably made the same ,as the minimum speevdilimitxot, isay,20

miles per hour. vThe .selection of the number ofi'loopsin acaution block, andthe speed limits enforced by each'loop is `'susceptible of to be Jfollowed out.

y au;

variation and adaptation -to fit dierent con- 'd1tions5 and it .should be understoodr'that the specific example just givendoes not have @Image fromcautz'loa tollear If, while the .,trainistraveling' in a caution blocln-fthisblo'ck. changes tofclear, dueto theremoval offthe danger condition in the blocky neXjtv inV advance, the. car relay MRlinstantl; responds, changingthe cab vsignal indications l and lrestoringthecar app aratus to thenormalY L condition. `Atthe .same timeall o1' the speed',

restrictions are instantly wiped lout, sincelthe j line-'phase current is. then conducted over the.V line wire 19 insteadloiiov-eri theline wireQQ-,

through the trackway speedloopsf yHence.

the engineer is immediately advised of, a;

change in traffic conditions aheadand isperj mitted to accelerata-*1" Emmy a angerufen Vthe train passesthe pointvB; near the; eXit.endofithe caution block, the :canrelay isv de-'energized,-` and the:V engineergis reff quire'dto acknowledge. the stop signal;V 'ThisA pontB will iotzcourse in practice be sufficient:

lyy conspicuousV to vthe:engineer4 ,toy enable;y him to makel thev acknowledgment 4at theV proper point, and iflv the; signal aheadv isv not visible to the'engineer from such'point;

Bl practice would dictatethe; {use of ,arepe'ater signal: It may be'expflained herethat the pointY B ,is .preferablyqlocated at least braking-distance for the minimum speed'fromfthel exit end of the block, so that albrake ap tion occurring: at this: point `Vdue; to

v plica- V ailure ofgthe engineer to acknowledge, will result in stopping thetrainlgshortof'the end of thel block;

VVlhen thecar -approacliesthe peint B, the; relay@ is venergized byits-,stick circuit, the fre,Y layi'IUsde-energzed, andtliarelfiy TDGR?? gized.y If a trainhas been properly governed Y and .istravelingf at some speed belowk the minimum speed, so that the speed'contacts 29-80 are "closed, andi the 'engineer in obedience to `the stopsignal indication oper- `9:373ontacts 36 of acknowledging contactor,

wire '94, finger 95 of relay Q and its front contact, wiresV 96 and 97, speed contacts 20-.50,Wire- 98, relay. S andwire 99V to C. VV-hen the fingers of the relay MR assume the cie-energized position, 'the .relay TU is ener gized; and with therelay S energized, a pick-up-circuit for the relay Q, isgestablished through the finger 100 of relay S and itsiront contactLwires:101`and86 and finger e7.L and the-iront contact of relay TU. Withithe re lays Q and S energized,jthe valve EPV is maintained energized bya circuitVromB, finger 102 otrelay and'its front contact, wire. 108, linger 104i ot'relay Qpandits front con-` tained energized, so long asl the speed is be- '109,and- 97, speed contacts-.29-30, wire 98,

relay S Tand wire 9,9 to C. With the relay energized, thecab indicator Ris lighted by a circuit whichcan be readily traced.

' Jil-.train maycontnue to travel through the danger or occupied block at'any speed below theminimum speed.y It this minimum speed limit-iis exceeded, the relay S is de-ener'gized, y and the brakes are automatically applied.V

then only if the contact 57 Vassociated iwiththe application valvel AVis closed and the speedy'k is low enough to vclose contacts 29.-30. c This pick-upcircuit maybe traced asffollowszbeginning atftle terminal B opt-a suitable bat- Y lovT the minimumlspeed limit and the car.l l

. 5 Therelay S is a stick relay,'itsrstick contact,

11g comprisingfcontact 108. IlthisStiCkrelay'S is kCle-energiz'edby reason otexcessive speedY 'resultingin opening con tacts.29+-30, it: can

1.1() only lbe picked up by acknowledgement'andf tery,. .contact. 57- ofthe v.brake application 1 valve Ali'wires 92a and 9,3, Contact 36 ofthe device AC, wireA 94, contact 95 ofthe relaynQ, (this relay being energized ifthe acknowledging kdevice AC, isfoperated andthe device.,

kAi'is in the brak-efapplyingr condition),

wires 96 and 97, contacts, E29'-30,'wire 98,- y

winding/o they relay S, wire y99, to the coni? y monreturn wire C to the other. side of said battery. j 'l f' tpointsr-Jwhere track switcheszareenr countered, itl isl desirable lteflprovi de suitable protection against the. possibility ot trains) runnnaon themaa tfaCkf-bilgfihwa into.-

a siding at an excessive speed, causing a derailnient` This is usually accomplished byl erated in accordance with the position ofthe track switch and are connected in some suitable control circuit, for instance the track circuit. In the present embodiment. it is assumed that the switch box contacts are connected in the track circuit in such a manner that if the switch is open, that is, set for a turn out move, the track circuit is broken and the block in which the switch is located becomes a danger block by reason ofthe deenergization of the track relay at its entrance end. n-ot by itself, constitute a part of the present invention.

If the track switch is set to its open position before an approaching train has entered the block in which the switch is located or the first block in the rear thereof, danger and caution control conditions will be set up in these two blocks respectively, and the train speed will be restricted in the manner described above in connection with the usual control in danger and caution blocks. If, however, the track switch is thrown to its open position while an approaching train is located in the first block to the rear of the block in which the switch is located, the engineer is given no warning as to the change of control conditions, and hence he can not acknowledge in time to prevent the de-energization of the electro-pneumatic valve, and an automatic brake application will result, bringing the train to a stop as described above in connection with passing a caution signal unacknowledged. Similarly, if the track switch is thrown to its open or turnout position while a train is traveling in the block inV which such switch is located, the engineer receives no warning and hence does not acknowledge, and the brakes are automatically applied until the train is brought to a stop as hereinbefore described.

From the above it is evident that the system of the present invention affords protection to an approaching train against the improper setting of a track switch, the extent of restriction imposed depending upon the location of the approaching train when the switch is improperly thrown. In this connection it should be observed that the same This siding protection does, howeverV rails, which flows'so asto inductively affect maintain the flow of control current because of interruptions in the continuity of the track rails at switch frogs, cross-overs, junctions between successive blocks and the like. In the systems of the invention, a brake application resulting from a momentary deenergization of the main relay MR is prevented bythe 'slow acting feature of the electro-pneumatic valve EPV, described above. The electro-pneumatic valve is preferably arranged to act so slowly that the longest iin-energized section of trackway ordinarily encountered may be traversed without the de-energization of the electro-pneumatic valve, provided the train is moving above a given speed.

As this invention has been described in a rather specific manner and in connection with several specic means and devices for carrying out its operation, it should be clearly understood that certain changes in such devices and apparatus could be made without departing from the scope of the invention. It should be further understood that certain well known eXpedients could be combined with the system of the present in-` vention without departing from its scope as defined by the appended claims.

What it is desired to secure by Letters Patent is 'l. In an automatic train control system of the type in which control influencesL corresponding to traffic conditions are continu-` ously transmitted from the trackway to a moving vehicle, carcarried apparatus comprising means for causing a brake application upon the transmission of influences corresponding to unfavorable traffic conditions, manually actuable means for suppressing said brake application if actuated before and released after the transmission of said unfavorable influences and trackway means comprising loops at spaced points having portions thereof locatedadj acent to the track rails and being energized under unfavorable traffic conditions to transmitv influences for limiting the speed of the vehicle to a predetermined value.

2. In an automatic train control system of the` type in which influences corresponding to traiiic conditions are continuously trans-p mitted from the trackway to aimoving vehicle, car-carried apparatusl for causing a brake application in response to influences corresponding to unfavorable traiicV conditions,

' manually,operablemeansfor preventing said v way* means in each block extending for dif-'lV ferent distances each setting up a lrestrictiv.e

brakev application if actuated before said inuences are received, and means for limiting the vehicle speedv underl unfavorable traflic` conditions to a. predetermined finite value comprisingtrack loops, energized under unfavorable traffic conditions,l and arranged vto transmit influences to a moving vehicle for a 'predetermined distance of its travel at spaced points. f f 3; In an automatic train-control system of the' type in which control influences corresponding totraflicconditions are continuously -transmittedto a moving vehicle from the trackwa-y, in combination with .the usual track' rails divided into blocks, spaced trackspeedl limit depending on the distance it extends if the next block in advance is occupied,

andE car-carried speed responsive means for limiting thel vehicle speed to a fixed value when the vehicle is travelingl in an occupied bl'ick.V f

1-.lin an automatic train control system,

"means" Vfor transmitting iniiuences corresponding yto traffic conditions continuously from the trackway to a moving vehicle, means :including Vspacedy trackway influence transmitting means oflimited extent for limiting the vehicle speed to afvalue depending on Y' such'ex'tent under caution traffic conditions, and" a car-carried speed responsive device for limiting Lthe vehicle speed to a safe valuev underA danger tra-Hic conditions.

5". In an automatic train control system of the typeY infwhich control influences correspending to traffic'conditions are continuously transmittedl inductively from the track' rails toial moving'veliicle, means for applying gtlie vehicle brakes upon the reception of influ'ences corresponding to caution or danger traiiic conditions, manually'actuable means for preventing such brake application if actuated beforea change' to unfavorable traiic .,coiiditions', spaced trackway means ofpredetermined extent lfor cooperating withy timed car-carried means to operate said brake applying means ifa givenfspeed is'cxceeded f under caution Ytraflic conditions,and a carcarried speed responsive device for causing the operation of said brake applying means Uifa given speed isv exceeded under danger traffic conditions.

6. Y]nan Lautomatic train control system of Vthe continuous'inductive type in which control influences are transmitted inductively from the trac'kway by current flowing in the track rails; in combination, a car-carried apparatus including a normally inactive brake control device", which has a tendency to assume its active condition, and means for preventing said brake'control device from becoming active tof apply the brakes if intermit- `tent control-'f influencesare receivedv induc- .tivelyfrom current `*flowing in they trackway,

said. last lmentioned means being inactive if the time of duration of said intermittent lconjin response toalternating current flowing in vthe track rails comprising, a normally inac- Atrol influences be less than'a ypredetermined value; and of'trackway Vmeans for intermit- 7o y tivev brake control device ona vehicle tending"- trol device becoming active; it control iniuencesY are continuously transmittedv from the trackway to the vehicle, and meansfor preventing said brake control device becomingl active if the vehicle speed is not excessive and if control influences 'are transmitted intermittently to the moving vehicle. in response to current flowing inl trackway circuits'including the track rails..v

8. A trainV control system ofthe continuous inductive' type in which control influencesjare Vtransmitted from the trackwayvto the'vehicle in response to alternating current of apar-v lticular frequency flowing in trackway circuits "including the trackrails ahead. of such-vehicle, a normally inactive brake control device on a vehicle tending to assume its active condition toapply the brakes, means for preventing said brake control device becoming vactive ir suchf alternating current influences arelcontinuously transmitted from the trackway, and means for preventing said brake controlA de- ,vice becoming active if the vehicle speed is not excessive and if alternating current infiuences of said' frequency aretransmitted intermittently tothe vehicle as it moves along the -tra'ckway in responseV to'alternating current flowing in such t-rackway circuits including such track rails. v l .y i

9.V In an automatic train control system ofthe type in which influencescorresponding to `traffic conditions are transmitted from the tra-c kway to a moving vehicle, a normally energized electro-pneumatic valve lforV exhausting a Huid pressure reservoir when dfi-energized and thereby initiating a brake application,` means` for die-energizing said valve in response to the transmission of infiuences corresponding to unfavorable trafficl conditions, and manually actuable means for maintaining said valve' energized if actuated while influences corresponding to favorabletraiiicconditions arebeing transmitted, said iiuid'pressure reservoir having a volume suolil that said brake application can noty be. released fofrla predetermined time sufl'icient* to bring the' lto assumel itsv active condition to apply the 1 brakes, means for preventing said brake conizo trainV to a stop ,with the brakes applied after said valve has been re-energized. Y

10.In an automatic train controlsy'stem, in combination with trackway means for continuously transmitting influences correspond. ing to traic conditions to a moving vehicle, car-carried apparatus comprising a normally energized brake control device adapted to initiate a brake application When cle-energized, a three-position main relay controlled in accordance with said influences to assume posi tions corresponding to clear, caution and danger traffic conditions and adapted to maintain said brake control device energized when in its clear position, an auxiliary energizingV circuit for said brake control device, a relay for closing said auxiliary circuit when energized, a pick-up circuit for said relay which is closed if a manually actuable circuit conf troller is actuated While said main relay is in its clear position, a stick circuit for said relay Which is closed only When said main relay is in its caution position, spaced trackvvay means for causing said main relay to assume its clear position under caution trafiic conditions for a predetermined distance of vehiclev travel, and means for closing an auxiliary circuit for maintaining said relay energized While said main relay assumes its clear position provided more Vthan a predetermined time interval is consumed by the train in traveling said predetermined distance, Whereby said brake control device is maintained energized and a brake application is avoided provided a given speed'is not exceeded under caution traffic conditions.

11. In an automatic train control system, in combination with trackway means for continuously transmitting inliuencesy corresponding to traflic conditions to a moving vehicle, car-carried apparatus comprising a normally energized brake control device adapted to initiate a brake application When de-energized, car-carried means controlled in accordance With said influences and adapted to maintain said ybrake control device energized under favorable trac conditions, an auxiliary device for maintaining said brake control device energizedvvhen operated, man-V ually actuable means for Voperating said auxiliary device if actuated before the reception of influences corresponding to unfavorable traffic conditions, and spaced trackWay means, active under unfavorable traihc conditions to release said auxiliary device and to cle-energize said brake control device if a predetermined speed is exceeded.

12. In an automatic train control system of the type in Which control influences corresponding to traiiic conditions are continuously transmitted inductively from the trackway to a moving vehicle, in combination with the usual track rails divided into blocks, carcarried apparatus comprising a normaly energizedbrake control device adapted toinnwiaeaa itiate a brake application vwhen deeenergized, car-carried means controlled in accordance with said influences and adapted to ,maii'r tain said brakecontrol device energized un-` der favorable traffic conditions, an auxiliary device for maintaining said brake control de: vice energized When operated, manually actuablemeansforoperating said auxiliary device if actuated before the reception of iniiuences coresponding to unfavorable traliic conditions, spaced trackvvay devices of lim'- ited extent, active, When the next block in advance is occupied, to release said auxiliary device and so to cle-energize said brake control device if a predetermined speed is exceeded, and a vehicle caried speed responsive device active when the vehicle is travelingV Vspeed responsive device for causing a brake application if a given speed is exceeded under more unfavorable traiiicconditions.

14. In an automatictrain control system of the type in which control influences corresponding to traflic conditions are transmitted from the trackvvay to a moving vehicle con tinuously through the medium Vof current flowing in the track rails, in combination With the usual track rails divided into blocks, spaced trackway means in each block for cooperating Withcar-carried apparatus toyset up increasingly restrictive .speed limits if the next block in 'advance is occupied, anda car-carried speed responsive device for limiting the vehicle speed to a fixed'value When theV vehicle is traveling in an occupied block.

15. In an automatic'train controlV system of the continuous inductive type, car-carried apparatus comprising a normally energized brake applying device, adapted When de-en ergized toinitiate a brake application, means for cle-energizing said brake applying device.

under unfavorable traiiic conditions, a normally de-energized stick relay, acting When energized to maintainsaid brake applying device energized undervunfavorable traflic conditions, a manually operable contacter 'for energizing said stick relay, and a timed contact associated With said contactor for cle-energizing said brake applying device if said ccntactor is maintained closed for more than a predetermined time interval.

16. In an automatic trainA control system of the type in which control inliuences corresponding te trat conditions are contnu-Y Onsly transmitted from the trackvvay to 'Y aL plying device, a manually operable contactor for energizing said stick relay if operated b'e- Vfore the reception of inliuences corresponding to unfavorablek traffic conditions, and

' means associated with said contacter for deenergizing said'brake applying device if said Y contacter is maintained closed for more than Y a predetermined time interval.

In testimony whereof I affix mySignature.Y

WADE n. REICHARD.

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